Mechanism for feeding granular or powdered material from a relatively low pressure to a higher pressure



July 12, 1955 T. EDWARDS 2,712,963

MECHANISM FOR FEEDING GRANULAR 0R POWDERED MATERIAL FROM A RELATIVELYLOW PRESSURE TO A HIGHER PRESSURE Filed Oct. 23, 1951 2 Sheets-Sheet lJuly 12, 1955 T. EDWARDS 2,712,963

, MECHANISM FEE G GRA AR OR POWDERED MATERIAL ROM A REL VELY W PRE RE TOA HIGHER PRESSURE Filed 061. 1951 2 Sheets-Sheet 2 ATTORNEYS UnitedStates Fatent Qfice 2,712 Patented July 12, 1955 Application Get l r 23,1951, eriai 1 9. 252,781

or. 392 m This invention has reference to improvements in mechanism forfeeding granular or powdered material from relatively low pressure to ahigher pressure and is particularly applicable for feeding granular orfinely powdered material from atmospheric pressure into a systemmaintained above atmospheric pressure, where the material to be fed isof an abrasive character as is the case, for example, with pulverisedfuels. It is usual with such mechanism to feed the material into the lowpressure side of a pump direct from a storage hopper, the fiow of powderwhen necessary being assisted by a conventional conveyor device and thepump itself conveying the material to a high pressure gaseous blast portwhere the powder is removed by the high pressure blast from the pumpbody to a delivery manifold. With such a design it is difficult tomaintain an effective seal between the high and low pressure sides ofthe pump where the material being handled is of an abrasive charactersince the sealing surfaces deteriorate rapidly due to the penetrationbetween them of the abrasive particles.

The present invention has for its object to provide a mechanism in whichthe high pressure delivery port is isolated from the low pressure oratmospheric feed point and wherein the sealing system is such that itwill accommodate itself to any wear due to abrasion between the workingsurfaces so as to automatically maintain the seal at normal workingefliciency and pressure diiferentials and further to provide means forreadily dismantling and replacing the working surfaces when necessary.

The invention consists of a mechanism for feeding granular or powderedmaterial from a relatively low pressure to a higher pressurecharacterised in the provision of a rotatable pocketed carrier plateeach pocket whereof is brought successively during the rotation of thecarrier plate, into a position to receive a charge of material atrelatively low pressure and then into a position so as to form aconnection between two ports one of which is adapted to receive a blastof gas at high pressure and the other of which is connected to the highpressure system to which the material is to be fed. The inventionfurther resides in features of the construction of the mechanism to bedescribed hereinafter.

In order that the invention may be clearly understood and readilycarried into practice reference may be had to the appended explanatorydrawings in which:

Fig. 1 illustrates the mechanism in vertical sectional elevation and 1Fig. 2 is a plan View with certain parts removed for clarity.

According to a convenient embodiment of the present invention themechanism comprises a rotatable carrier plate a mounted for rotationabout a vertical axis being keyed to the vertical shaft 5 housed withina casing 'c. The shaft b is coupled to a motor driven variable speedgear, not shown, and preferably at b In the car rier plate are a numberof pockets a of rectangular or other section, see particularly Fig. 2,which act as carriers for conveying the powdered or granular materialfrom atmospheric pressure at the feeding point of the mechanism to thehigh pressure delivery manifold d, see particularly Fig. 2.

The material to be fed to the pockets a in the carrier plate a may befed by gravity from a vibrating feeder in turn receiving the materialfrom a hopper, not shown, so as to give a continuous or semi-continuousfeed to the mechanism at d. This feeding system can if required functionas a metering device in which case the carrier plate a is rotated at aconstant speed such that the potential rate of feed of the mechanism isin excess of the rate of feed thereto by the vibrating feeder. Thevibratfeeder incorporates a calibrated infinitely variable controlpermitting any predetermined quantity of material to be fed to themechanism so that adjustment of this control gives rapid change in thequantity of material being fed into the high pressure system and sincethe control is calibrated the delivery of material is set at a definitefeeding rate to an accuracy of within plus or minus 2%. If a moreaccurate control of feed rates is required then a continuous type ofweighing machine may be introduced between the hopper and the vibratingfeed. Alternatively the mechanism itself will function as a lessaccurate meter by varying the speed of rotation of the carrier plate it,having first adjusted the primary feeding device (i. e. the vibratingfeeder and/or a continuous type of weighing machine) to ensure that thepockets in the plate are filled to capacity.

The pockets :2 in the carrier plate a are in the form of ports passingvertically through the plate as illustrated but each is closed at itslower end by a lightly spring loaded poppet valve, the spring being sodisposed as to hold the valve closed during the filling and conveyingperiod. Snce the valve operates at a very low pressure difference it is,therefore, to be preferred to a porous filter which may be used andwhich serves to retain the material in the pocket a As the carrier plate11 rotates the pockets a are successively charged with material from thefeeding point d and may then pass under a series of scrapers which areadapter. to remove any superfluous material deposited around the edgesof the pockets. From beneath the scrapers the pockets a pass between twosealing pads e and f held in contact with the carrier plate by spring ror pneumatic or other pressurised loading; one of these pads 6 beingdisposed above the plate and the other f beneath. The two pads areprovided each with one of a pair of aligned ports e f forming part ofthe high pressure system of the mechanism and of a size and section tocorrespond to the section of the pockets a in the main carrier plate a,the pockets being so designed as to provide whatever lap or lead may benecessary to ensure efficieat evacuation of the material from the pocketby upward blast from the pipe and With due regard to the size of theparticles and characteristics of the material to be fed. Both sealingpads, e and which are preferably circular, are designed to cover threeor more pockets :1 in the carrier plate a at one time and the port inthe upper pad e is connected to the main delivery line it to the highpressure system to be fed, whilst the port f in the lower pad isconnected to the high pressure source from which the gaseous blast isreceived. As each pocket 0 passes between the aligned ports e f of thesealing pads e and 7 the high pressure blast enters the pocket throughthe poppet valve a and carries the material into the main delivery lineI: where it is piped to the required point of the high pressure system.The gaseous blast is always maintained at a pressure in excess of thepressure of the receiving system so as to efiect rapid and completeevacuation of the material from the pockets. As a pocket a continues itsrotation from the delivery point between the sealing pads in and n itenters i to atmosphere.

pipes can be connected to the main powder storage hopper a scavengingsection j, see particularly Fig. 2, where clean air is blown or drawnthrough the pocket a to expel any condensate remaining as the result ofthe blast,

this section being especially important Where steam is utilised for theblast. Where the scavenging section is connected to a vacuum pump thenthe ports controlling the scavenging are so disposed that cut off on theatmospheric port occurs before cut off from the vacuum port so as toensure that there is a negative pressure in the pocket as it re-entersthe filling position, thereby assisting the filling operation andpreventing blow back. 7

As previously mentioned, the sealing pads e and f are held against thecarrier plate a by spring or pneumatic or other pressurised loading.With the spring system, varying pressures may be applied to correspondto the high pressure side of the plant by means of an adiusting screw,and furthermore the spring loading has to be adjusted to correspond withthe delivery and blast pressure. On the other hand, when the discs areloaded pneumatically or hydraulically, the pressure of the sealing padon the carrier plate is automatically maintained at the correctproportionate sealing pressure.

The sealing pads which are located in a suitable housing containing theblast and delivery pipes are flexibly mounted so as to accommodate anymisalignment.

The actual sealing surface of the pads e and 1 may be plain or fittedwith such lubricating and/or exhaust ports as may be required. Theexhaust ports when used are so placed as to relieve instantaneously theblast pressure remaining in the pockets after the powder has beenevacuated, and are connected by pipes as indicated at i Where a dryblast is used .then these to deposit any entrained powder containedtherein.

The sealing pads e and f are adapted to be rotated slowly about thecentral axes of their ports, by an internally or 'externallymounted geardrive k and l during therotation of the carrier plate. This slowrotation ensuresthatthe discs wear evenly and lap themselves in with thecarrier plate.

Hard material is chosen for the carrier plate a for example, ,hardchromium plating, nitriding, or special alloy steels. On the other handthe sealing pads are constructed with materials having softerproperties; for example, bronze or aluminum lignum vitae. Wear,therefore, takes place only on the sealing pads, such Wear beingautomatically accommodated by the spring or other loading system so asto maintain the seal atits normal working efliciency. The sealing padand methods of housing are so designed as to permit rapid replacement ofthe sealing pads, if and when necessary.

In addition to the sealing pads e and f in contact with the main carrierplate a there are two stationary cast iron or bearing metal discs m andn which are held from the. main housing 0. These secondary sealing discsserve as an additional seal surrounding the sealing pads e and f as aprecaution against blow-back in the event of any break-down of thesealing pads. The pressure of. the secondary sealing discs upon theupper and lower sides of the carrier a is adjustable by means ofthreaded caps p which may be screwed inwardly or outwardly to more orless compress springs 2 The cap at the scavenging section shown in Fig.2 has an opening through its top to permit the exit of a scavengingblast as each pocket passes a hole in the disc m directly beneath thecap.

"The housing 0 of the mechanism is fitted With a material 'feeding duct0 located immediately above the pockets of the carrier plate at thefeeding point and extending in the same. radius'and concentrically forsuch length as to enable the pockets to be completely filled and inorder thatrthe powder shall be directed to the centre of'the pockets,the width of the feeding duct is less than the radial dimensioniof thepockets. The feeder port is a vertically sliding fit 'in the housing andis spring loaded to maintain contact with the carrier plate.

As an alternative to the mechanism described, the pockets in the carrierplate may be of U form in which case the blast inlet port and the outletport to the main delivery line to the high pressure system are containedin the one pad. As a further alternative the carrier plate may bemounted to rotate about a horizontal axis and the pockets formed aroundthe periphery thereof, in' this case the sealing pad is in the form ofan arcuate shoe resiliently pressed against the periphery of the carrierplate and may contain both inlet and outlet ports to registerrespectively with opposite limbs of U-shaped pockets in the periphery ofthe carrier plate or the shoe form of pad may contain either one of theinletor outlet ports the other of which is contained in a second padbearing against the face of the carrier plate in a similar manner tothat described in the first embodiment described, in this latter casethepocket in the carrier disc would be L shape.

I claim:

1. Mechanism for feeding granular or powdered material frorn lowpressure environment into high pressure said sealing member about anaxis passing through said blast inlet port.

2. Mechanism for feeding granular or powdered material from low pressureenvironment'into high pressure environment comprising a rotatablecarrier, a sealing member having a surface slidingly engaging a surfaceof said carrier, said carrier having a series of pockets, each of saidpockets having an opening to receive such material and from which suchmaterial can be discharged,

each of said pockets also having a blast inlet valve,

means for supplying such material to said pockets in low pressureenvironment, said sealing member having a blast inlet port located toregister successively with said blast inlet valves as said carrier isrotated, means for moving said sealing member about an axis passingthrough said blast inlet port, anda second sealing member having anoutlet port located to register successively with the openings of saidpockets as said carrier is rotated.

3. Mechanism'for feeding granular or powdered material from low pressureenvironment into high pressure 7 environment comprising a rotatablecarrier, a sealing member having a surface slidingly engaging a surfaceof said carrier, said carrier having a series of pockets, each of saidpockets having an opening to receive such mate rial and from which suchmaterial can be discharged, each of said pockets also having a blastinlet valve, means for supplying such material to said pockets in lowpressure environment, said sealing member having a blast inlet portlocated to register successively with said blast inlet valves as saidcarrier is rotated, means for moving said sealing member about an axispassing through said blast inlet port, a second sealing member having anoutlet port located to register successively with the openings of saidpockets as said carrier is rotated and means for moving said secondsealing member about an axis gaging surfaces of said carrier, andsealing members together to prevent the egress of high pressure fluidtherebetween.

5. Mechanism for feeding granular or powdered material from low pressureenvironment into high pressure environment comprising a rotatablecarrier, a sealing memher having a surface slidingly engaging a surfaceof said carrier, said carrier having a series of pockets, each of saidpockets having an opening to receive such material and from which suchmaterial can be discharged, each of said pockets also having blastadmitting means, means for supplying such material to said pockets inlow pressure environment, said sealing member having a blast inlet portlocated to register successively with the blast admitting means of saidpockets as said carrier is rotated, means for moving said sealing memberabout an axis passing through said inlet port, and a stationary padsurrounding said sealing member and said inlet port and also having asurface engaging a surface of said carrier.

6. Mechanism for feeding granular or powdered material from low pressureenvironment into high pressure environment comprising a rotatablecarrier, a sealing memher having a surface slidingly engaging a surfaceof said carrier, said carrier having a series of pockets, each of saidpockets having an opening to receive such material and from which suchmaterial can be discharged, each of said pockets also having blastadmitting means, means for supplying such material to said pockets inlow pressure environment, said sealing member having a blast inlet portlocated to register successively with the blast admitting means of saidpockets as said carrier is rotated, means for moving said sealing memberabout an axis passing through said inlet port, and a stationary padsurrounding said sealing member and said inlet port and also having asurface engaging a surface of said carrier, there being a second padsurrounding the second sealing member and also having a surface engaginga surface of said carrier.

References Cited in the file of this patent UNITED STATES PATENTS941,024 Mantius Nov. 23, 1909 1,321,262 Townsend Nov. 11, 1919 2,084,764Constantin June 22, 1937 2,299,565 Colburn Oct. 20, 1942 2,314,031Colburn Mar. 16, 1943 2,585,472 Kennedy Feb. 12, 1952 2,592,815 LukesApr. 15, 1952 2,614,891 Colburn Oct. 21, 1952

